The present invention relates to a method of tuning a vehicle engine induction and exhaust system and corresponding vehicle sound transmission paths.
There are many noise sources in a vehicle. For example, there is structure born noise such as vibrating body panels. In addition, there is noise from the vehicle air in/out system. The noise produced by the various noise sources of the vehicle travels to the vehicle interior where some of the noise is heard by vehicle occupants. To enhance the vehicle image, it is important that the noise heard by the occupants is consistent with the image of the vehicle, i.e., sound of power for a sports car, quiet pleasing sound for a luxury vehicle, etc.
For the foregoing reasons, there is a need for a method of tuning the induction and exhaust system and corresponding vehicle sound transmission paths that improves over some existing vehicle noise vibration harshness (NVH) processes.
It is, therefore, an object of the present invention to provide a method of tuning a vehicle that considers the effects of the phase angle of the noise from different noise sources.
In carrying out the above object, a method of tuning a vehicle having an interior and an engine operable over a range of engine speeds is provided. The engine has an air in/out system including an induction system inlet and an exhaust system outlet. The method comprising measuring a plurality of inlet frequency responses at the inlet port to a plurality of different engine speed inputs. Each inlet response includes an amplitude response and a phase response. Further, a plurality of outlet frequency responses at the outlet port to a plurality of different engine speeds inputs are measured. The method further comprises determining an inlet transfer function and determining an outlet transfer function. The inlet transfer function generates a frequency response, including an amplitude response and a phase response, at the vehicle interior to an input at the inlet port. The outlet transfer function generates a frequency response, including an amplitude response and a phase response, at the vehicle interior to an input at the outlet port. The method further comprises determining an interior noise spectrum based on the plurality of inlet frequency responses, the inlet transfer function, the plurality of outlet frequency responses, and the outlet transfer function. And, the engine air in/out system is modified based on the interior noise spectrum to result in a different interior noise spectrum.
In a preferred embodiment, measuring the plurality of inlet frequency responses further comprises, for each different engine speed input wherein adjacent engine speeds in the plurality of engine speeds are about 50 rpm apart from each other, measuring the inlet response at a plurality of different frequencies in the audible spectrum. Adjacent frequencies at which the inlet response is measured are about 2 Hz apart from each other.
Further, in a preferred embodiment, measuring the plurality of outlet frequency responses further comprises, for each different engine speed input wherein adjacent engine speeds in the plurality of engine speeds are about 50 rpm apart from each other, measuring the outlet response at a plurality of different frequencies in the audible spectrum. The adjacent frequencies at which the outlet response is measured are about 2 Hz apart from each other.
A suitable inlet transfer function may be determined by measuring an interior frequency response to a white noise input at the inlet port. A suitable outlet transfer function may be determined by measuring an interior frequency response to a white noise input at the outlet port. In a preferred embodiment, determining the interior noise spectrum further comprises multiplying the plurality of inlet frequency responses by the inlet transfer function, in the frequency domain, to product a first plurality of interior frequency responses. Then, the plurality of outlet frequency responses are multiplied by the outlet transfer function, in the frequency domain, to produce a second plurality of interior frequency responses. And, the first and second pluralities of interior frequency responses are added to produce a third plurality of interior frequency responses.
It is appreciated that modifying the engine air in/out system may be performed in a variety of ways to achieve desired sound quality within the vehicle. For example, in some implementations it may be desirable to modify the engine air in/out system so that the resulting different internal noise spectrum emphasizes frequencies that are multiples of the engine firing frequency. Of course, in accordance with the present invention, the air in/out system may be modified to emphasize any particular frequencies, as desired. The engine air in/out system may be modified in many ways. For example, an expansion chamber, a quarter wave resonator, or a Helmholtz resonator, or any combination of these elements may be added to the air in/out system.
The advantages associated with embodiments of the present invention are numerous. For example, a method of tuning in accordance with the present invention considers both of the amplitude response and the phase response at both the inlet port and the outlet port of the air in/out system. In addition, the inlet transfer function and the outlet transfer function generate both amplitude and phase responses. By considering the effects of phase angle, embodiments of the present invention improve upon some existing techniques for tuning vehicles.
The above object and other objects, features, and advantages of the present invention will be readily appreciated by one of ordinary skill in the art in the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.